Subject: Space-tech Digest #101 Contents: GPS beyond LEO? Art Dula & the Soviets Info on orbital debris Electromechanical actuators (2 msgs) Aerogels (3 msgs) How much work to convert RP-1 engine to methane? (9 msgs) OMV (2 msgs) ------------------------------------------------------------ Date: Mon, 10 Feb 92 15:50:32 PST From: David.Michelson@mtsg.ubc.ca To: space-tech@cs.cmu.edu Subject: GPS beyong LEO? In an earlier post, I enquired about the possibility of positioning satellites in GTO and GEO using GPS. GPS is, of course, very suitable for use by satellites in LEO... So far, I've only found one reference that deals explicitly with this problem: G. Barresi et al., "Autonomous navigation of small coorbiting satellites using C/A GPS code." Small-Satellite Technology and Applications, B.J. Horais, Ed., Proc. SPIE 1495, pp. 246--258, 1991. On page 252, they note that: "Unfortunately, the beamwidths of the GPS signals are barely sufficient to cover the earth, extending no more than 3000 km beyond the limb as viewed from GPS. Thus, users above 3000 km, which spend some time outside of the beams of GPS satellites otherwise visible to them, can suffer a degradation in performance..." If anyone has anything else to share on this matter, please do so! Dave Michelson "davem@ee.ubc.ca" ------------------------------ Date: Thu, 13 Feb 92 08:53:56 CST From: schatz@chaos.utexas.edu (Mike Schatz) To: space-tech@cs.cmu.edu Subject: Art Dula & the Soviets I am looking for information on the company (run by a Houston lawyer, Art Dula) that was serving as a liasion between the Soviet space program and Western customers (companies, universities, etc.) that desired access to Earth orbit. It is my understanding that Dula had something like an exclusive license with the Soviets to act in this capacity. Does anyone know the status of Dula's operations now that the Soviet Union is no more? Any information (historical background or current) would be greatly appreciated. Thanks Michael Schatz schatz@chaos.utexas.edu ------------------------------ From: Rudy Cazabon x2203 Date: Fri Feb 14 13:44:57 1992 Subject: Info on orbital debris To: space-tech@cs.cmu.edu I received the mail message stating the purpose and scope of this group. I am interested in knowing if any of you who pariticpate in this newgroup are currently doing active research in the area of orbital debris. If you are please answer back with you name, organization, and a short description of what your activities are. It is my interest to pursue research activities as a graduate student in this area and any guidance you could offer on this topic would be greatly appreciated. I am aware of the problems involved in detecting debris fragments in the 1 mm - 10 cm range by optical and radar techniques. If you are currently working on detection techniques I would interested in hearing from you. Thank you for your time. Rudy Cazabon jungla@talis4.UUCP ------------------------------ Date: Thu, 13 Feb 92 14:14 GMT From: CSG0669@vax2.queens-belfast.ac.uk To: SPACE-TECH@cs.cmu.edu Subject: Electromechanical actuators [ Regarding George Herbert's thrust vectoring ideas from a while back... ] I don't think hydraulics are a priori necessary. You can get some rapid electromechanical actuation that is fairly strong. In the case of thrust vanes you might not need to even move through a very high angle anyway. Note that the DCX presentation specifies use of electro-mech actuators as a time saver for turn around. ie, no APU's... I'm NOT saying NO hydraulics, just don't think the really heavy duty APU types are required if you keep the vehicle size in reason. Dale ------------------------------ Date: Sun, 16 Feb 92 19:59 CST From: moe@nuchat.sccsi.com (Norman C. Kluksdahl) To: space-tech@DAISY.LEARNING.CS.CMU.EDU Subject: use of EMA (electro-mechanical actuators) My wife is in the propulsion and power division at JSC, and she is heading an effort to use EMA for next-generation vehicles. EMA is very feasible, provided you can get the power you need; some EMA is VERY power-hungry. There seems to be no trouble with getting the required range or rate of motion. One of the avionics lads was very interested in an 'electric orbiter' using EMAs instead of APUs. This was seriously considered for Endeavour, especially after 2 consecutive flight problems with hydraulics: one flight leaked 1 or 2 gallons of hydraulic fluid in the aft compartment; another flight had an APU overheat on descent. When that happened, the EMA project got some serious evaluation. Alas, it was dropped. (The other vehicles would have been refitted with EMA at a later date) EMA is now being studied primarily for new vehicles. As I said, you have to ensure that you can carry enough energy source, and that it is rated to deliver LOTS of power in a very short time. N. Kluksdahl ..!nuchat!moe ------------------------------ From: tneff@bfmny0.BFM.COM (Tom Neff) Date: Wed, 19 Feb 1992 14:03:09 EST X-Mailer: Mail User's Shell (7.1.1 5/02/90) To: space-tech@cs.cmu.edu Subject: Aerogels Have y'all been following the development of aerogels, a.k.a. "frozen smoke"? They sound pretty exciting. I keep hearing about them at intervals, most recently that NASA is planning to use some to collect space dust without damaging it. One of my magazines this week has a nice picture of a handful of frozen blue smoke with a 100g weight sitting on top of it and a readable US penny behind it. I wonder whether properly-made aerogels might be the perfect space shield? ------------------------------ Date: Thu, 20 Feb 1992 08:26:16 -0600 From: Fraering Philip G To: space-tech@cs.cmu.edu Subject: re: aerogels Actually, what about a system that suddenly deposits charge on an approaching mote of space dust? It should significantly alter its orbit for a bit, thanks to the local magnetic field... Phil ------------------------------ Date: Tue, 25 Feb 92 11:58 PST From: trost@reed.edu (Bill Trost) To: Tom Neff Subject: Aerogels cc: space-tech@cs.cmu.edu Well, I didn't see you get any good responses on this, so you'll have to get mine instead. :-) My wife did a little playing around with aerogels for her undergraduate thesis. While they material can support large amounts of weight and weighs very little, it is very brittle. Simply passing a small one around a medium-sized classroom almost guarantees that what you get back is two or more smaller aerogels. It tends to cleave off chunks given the opportunity. Or, in other words -- I doubt they'd make a good shield for very long.... On the other hand, there are ideas of using aerogels inside rocket fuel tanks or between double-pane windows. You can store large quantities of stuff inside an aerogel, and it increases the structural strength of the container (you may be able to get higher pressures as well -- I'm not clear on that). The double-pane window case is more dramatic, as it will let you create gigantic double-pane windows that are seperated by only a little bit without fear of it sagging together and losing your insulating space. ------------------------------ From: sequent!techbook.com!szabo@uunet.UU.NET (Nick Szabo) Subject: How much work to convert RP-1 engine to methane? To: space-tech@cs.cmu.edu Date: Thu, 20 Feb 92 1:43:36 PST How much work would be required to convert an RP-1/LOX engine to burn CH4/LOX or methanol/LOX? I am looking for a rocket engine to work in a situation where methane is plentifully available, but H2 and complex hydrocarbons are not. The engine should have a long lifetime and be restartable. ------------------------------ From: henry@zoo.toronto.edu Date: Thu, 20 Feb 92 16:56:20 EST Subject: Re: How much work to convert RP-1 engine to methane? To: space-tech@cs.cmu.edu >How much work would be required to convert an RP-1/LOX engine >to burn CH4/LOX or methanol/LOX? ... I fear it's potentially quite substantial. The biggest problem is that the density will be different, which will affect pump design, injector hole size, and a long list of other things. Vaporization properties will be different, which will affect injector design and possibly combustion stability. Cooling properties will be quite different. RP-1 engines often use fuel as hydraulic fluid and/or lubricant, which might not work so well with the others. In the case of CH4, cryogenic fluid where there used to be room-temperature fluid will affect things like lubrication in valves and thermal-expansion provisions everywhere. In the case of methanol, one would have to check carefully for problems with chemical breakdown at high temperatures in cooling passages. All that being said, these are things that *might* go wrong rather than things that *will* go wrong. There is some chance that you could get away with it, especially if you didn't push the engine too hard. I would not want to make any promises without trying it. Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: Thu, 20 Feb 1992 15:58:11 -0600 From: Fraering Philip G To: space-tech@cs.cmu.edu, szabo@techbook.com Subject: Re: How much work to convert RP-1 engine to methane? Might just be simpler to chain the hydrocarbons together with an attached converter of some sort... Phil ------------------------------ Date: Thu, 20 Feb 92 15:32:56 PST From: gwh@lurnix.COM (George W Herbert) To: pgwres01@ucs.usl.edu, space-tech@cs.cmu.edu Subject: Re: How much work... Phil, one question... How do you propose to convert methane to long-chain hydrocarbons, on the fly, with an "attached converter" ? 8-) -george william herbert gwh@ocf.berkeley.edu gwh@lurnix.lurnix.com ------------------------------ Date: Thu, 20 Feb 1992 18:12:57 -0600 From: Fraering Philip G To: gwh@lurnix.com, pgwres01@ucs.usl.edu, space-tech@cs.cmu.edu Subject: Re: How much work... I don't know... try to find a chemist. Aren't plastics chained together from shorter-chain hydrocarbons? Let me see... I suppose... It may or may not be what Nick wanted, but you could break some of the stuff apart into hydrogen and carbon, make water, dump the carbon into a "bed" of calcium, heat it, and use the result to make acetylene gas... burn it in a combustion chamber, perhaps feeding in some of the leftover H2 to lower the moleculat oops, molecular weight, and voila! Sorry folks, I'm not even speculating right now, just brainstorming... Is there a chemist in the house? Phil ------------------------------ Date: Fri, 21 Feb 92 01:05:01 EST From: dietz@cs.rochester.edu To: gwh@lurnix.com, pgwres01@ucs.usl.edu, space-tech@cs.cmu.edu Subject: Re: How much work... > Aren't plastics made from ... shorter hydrocarbons? Yes, but not methane! Polyethylene is made from ethylene, for example. In general, it is much easier to crack larger hydrocarbons down to shorter ones than to join C-1 compounds. There is a process, the Fischer-Tropsch process, that converts syngas (CO + H2) to higher hydrocarbons and alcohols. One can make syngas from methane and steam. The whole process is pretty complicated, though, and not enormously efficient. Oil companies would really like a cheap way to activate the C-H bonds in methane for direct conversion to C-2 compounds. It's something a holy grail. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ From: henry@zoo.toronto.edu Date: Fri, 21 Feb 92 02:46:41 EST To: Fraering Philip G Cc: gwh@lurnix.COM, pgwres01@ucs.usl.edu, space-tech@cs.cmu.edu Subject: Re: How much work... >Is there a chemist in the house? I don't quite qualify, as I only got about 2/3 of the way to a chemistry degree before being seduced by the dark side of the electromagnetic force (computers), but I'll try anyway... Making higher hydrocarbons from methane is, basically, very hard. Oversimplifying somewhat, carbon's unique position in chemistry comes about because it forms bonds with itself about as willingly as with other things. If it formed bonds with other things more willingly, a la silicon, you'd never get long carbon chains, while if it formed bonds with itself more willingly, a la nitrogen, it would lock itself up in tight little molecules and never acquire all those side groups that do all the biochemical work. The problem with this is that it's really hard to put long carbon chains together out of single atoms. Almost anything that will break side groups loose, freeing carbon bonds to hook up to other carbon bonds, will also break up the new carbon-carbon chains. Industrial polymerization relies heavily on making or finding short carbon chains with double bonds, which are fairly easily induced to hook to each other and only to each other. If you can get from methane -- one carbon alone -- to ethylene -- two carbons connected by a double bond -- you are home free. That first step is a killer. Find a cheap and easy process to do it and you can make enough money to start your own space program. I'd be very surprised if conversion of methane to higher hydrocarbons was practical as a method of in-the-field refuelling. Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ From: henry@zoo.toronto.edu Date: Fri, 21 Feb 92 11:13:52 EST To: space-tech@cs.cmu.edu Subject: engine conversion On the bright side, I've recently run into a reference to a successful conversion of a kerosene engine to hydrogen, done for experimental work early in J-2 development. No indication of difficulties or quality of results, and I don't believe it was ever flown, but it suggests that such conversions are not hopeless. (Hydrogen is in many ways a much more difficult case than methane or methanol.) Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ From: hsv3!mvp@apple.com (Mike Van Pelt) Subject: Re: How much work... Date: Fri, 21 Feb 1992 01:30:25 GMT Apparently-To: space-tech@cs.cmu.edu To: space-tech@cs.cmu.edu In article <199202210012.AA20065@armagnac.ucs.usl.edu> pgwres01@ucs.USl.EDU (Fraering Philip G) writes: >I don't know... try to find a chemist. Aren't plastics chained >together from shorter-chain hydrocarbons? It could be done in a factory. I don't know offhand of any likely way to do it in a converter attached to a rocket. -- The powers not delegated to the United States by the | Mike Van Pelt Constitution, nor prohibited by it to the States, are | Headland Technology/V7 reserved to the States respectively, or to the people.| ..ames!vsi1!hsv3!mvp U. S. Constitution, Amendment 10. (Bill of Rights) | mvp@hsv3.lsil.com ------------------------------ Date: Fri, 21 Feb 92 09:09 PST From: trost@reed.edu (Bill Trost) To: space-tech@cs.cmu.edu Subject: OMV Can someone give me the "scoop" on the OMV? I've heard rumors that NASA scrapped it for a cheaper "Orbital Transfer Vehicle" -- whatever that means? Anyone here know what I'm talking about (since I clearly don't :-) )? ------------------------------ Date: Sat, 22 Feb 92 13:35:54 CST From: eder@hsvaic.boeing.com (Dani Eder) To: trost@reed.edu Subject: Re: OMV Cc: space-tech@cs.cmu.edu The term 'OMV' usually refers to a space tug for moving among low Earth orbits (the spec used to read up to 1000NM altitude or 7 degrees of plane change). It was originally supposed to have cost $400M to develop and fly by 1989. About a year or two ago they cancelled it having spent $900M and they weren't done yet. The Orbit transfer vehicle (OTV) has gone through preliminary studies at least 4 times since 1972, but has never gotten to be a real program. It was always envisioned as a much more capable space tug, to take large payloads to Geosynchronous orbit and such. Dani ------------------------------ End of Space-tech Digest #101 *******************